The invention relates to a seam welding machine for joining together with a seam weld sheet blanks clamped side by side, comprising
a welding arrangement defining a weld axis, PA1 two clamping blocks arranged on either side of the weld axis for the sheet blanks, each with upper and lower pressure beams and upper and lower clamping devices defining a receiving gap for the sheet blanks and, PA1 a longitudinal transport system for advancing the clamped sheet blanks in the direction of the weld axis.
Seam welding machines of this kind are used in particular for the production of body blanks, often involving the joining together of sheet blanks of different grade and/or thickness. Before the sheet blanks are clamped in the clamping blocks of the machine, the sheet edges which are to be welded must be precisely aligned in relation to one another and to the weld axis, and this alignment must be sustained during the longitudinal feed, i.e. during the welding process, in order not to impair the quality of the welded seam. Account has to be taken of the fact that the workpieces may be subjected to considerable transverse forces in the course of welding, particularly in the case of mash seam welding between electrode wheels. Furthermore, in the case of seam welding by laser beam, the butting edges which are to be welded have to be held together with high transverse forces.
In a known welding machine of the aforesaid kind, a carriage, guided on the machine bed and capable of being longitudinally traversed as a complete unit, is provided for clamping and advancing the sheet blanks U.S. Pat. No. 5,081,331 . The carriage essentially has four (two lower and two upper) pressure beams provided with the clamping devices, with hydraulic clamping cylinders fitted in each of the upper beams. With this type of construction the pressure beams can only be joined together at their ends. The beams themselves must therefore be rigid enough in their construction not to be subject to unacceptable deformations due to the (both vertical and horizontal) forces exerted on them during clamping and welding. In practice, therefore, the overall length of the clamping blocks -- and hence the length of the welded seams which can be produced -- is somewhat limited, since to increase the length still further a carriage of disproportionately large dimensions, and corresponding weight, would be required. In addition the hydraulic clamping cylinders fitted to the traversing carriage must be connected via flexible pressure hoses, involving additional expense and possible complications.